An insulated gate type field effect transistor having a gate electrode with a gate insulating film being interposed is called a MIS transistor. If the gate insulating film is basically a silicon oxide film, this transistor is called a MOS transistor. A gate insulating film of a MIS transistor is not limited to a silicon oxide film, but may be a silicon oxynitride film or a laminated structure having a high dielectric film such as a HfSiO film laminated on a silicon oxynitride film. A gate electrode is not limited to a polysilicon film, and may also be an amorphous silicon film, a polycide film which laminates a silicide film on a polysilicon film, or a metal film.
Speeding up the operation of a MOS transistor has been realized conventionally by miniaturizing the MOS transistor in accordance with the scaling law. As a gate oxide film is thinned in conformity with the scaling law, leak current becomes large correspondingly. If leak current is to be suppressed, miniaturization of a MOS transistor does not necessarily result in high speed operation.
As technologies not dependent upon miniaturization for speeding up, so-called strain technologies (also called strained silicon and the like) have been paid attention. The strain technologies are an approach to improving a carrier mobility by applying compressive or tensile stress to a channel by some means. For example, it has been proposed to improve hole mobility by applying compressive stress to a channel region by embedding a silicon germanium (Si—Ge) layer having a lattice constant larger than that of Si in part of the source/drain regions of a p-channel type MOS field effect transistor (pMOSFET) formed by using a Si substrate (refer to JP-A-2006-186240).
If MOS field effect transistor is a n-channel type (nMOSFET), electron mobility can be improved by embedding a silicon carbon (Si—C) layer having a lattice constant smaller than that of Si in part of the source/drain regions.